Rollermills

ABSTRACT

A rollermill having a pair of grinding rolls, one of which is to be driven at a lower speed than the other, characterized in that the drive to the lower speed roll is taken from the higher speed roll by an endless member such as a belt or chain which drives the input shaft of a reduction gear box at a speed higher than that of the higher speed roll, the output shaft of the reduction gear box being connected with the lower speed roll. During separation of the rolls drive is maintained and belt or chain tension is automatically maintained constant.

Fullalove et a1.

ROLLERMILLS Inventors: Richard Fullalove, Manchester;

Frederick Spencer, Stockport, both of England Assignee: Henry Simon Limited, Stockport,

Cheshire, England Filed: Feb. 8, 1974 Appl. No.: 440,865

Related U.S. Application Data Continuation-impart of Ser. No. 219,454, Jan, 20, 1972, abandoned.

Foreign Application Priority Data Mar. 2, 1971 United Kingdom 5800/71 References Cited UNITED STATES PATENTS 3/1945 Smith et a1 74/242.l5 R

[ May 20, 1975 2,396,860 3/1946 L66 74/242,15 R 2,736,504 2/1956 Hannes. 241/232 2,826,300 3/1958 ROSS 241/232 X 3,238,802 3/1966 Bydzyn 74/219 3,240,436 3/1966 Mylting 241/230 3,412,769 11/1968 Howard 241/227 X 3,622,083 11/1971 Greenewald 241/227 X Primary ExaminerGranville Y. Custer, Jr. Assistant Examiner-Howard N. Goldberg Attorney, Agent, or Firm-Norris & Bateman [57] ABSTRACT A rollermill having a pair of grinding rolls, one of which is to be driven at a lower speed than the other, characterized in that the drive to the lower speed roll is taken from the higher speed roll by an endless member such as a belt or chain which drives the input shaft of a reduction gear box at a speed higher than that of the higher speed roll, the output shaft of the reduction gear box being connected with the lowerspeed roll. During separation of the rolls drive is maintained and belt or chain tension is automatically maintained constant.

14 Claims, 4 Drawing Figures ROLLERMILLS This is a continuation-in-part of pending application Ser. No. 219,454 filed Jan. 20, 1972, now abandoned.

This invention concerns rollermills of the kind used for milling wheat, maize or other materials capable of being ground by such a machine.

As is well known, a rollermill essentially includes a pair of grinding rolls, one of which is driven at a slower speed than the other, the material to be milled being progressed through the nip between such rolls. As is also known, means are usually provided to enable separation of the rolls, while they are being driven. in the absence of stock to be milled.

It is a normal practice for the roll which is driven at the lower speed to be driven from the other roll via a suitable reduction drive system. It will be understood that when milling there is a high torque in the drive system on account of the mechanical work being performed at the interface between the grinding rolls. Various kinds of drive systems have been proposed. Thus, a direct belt drive between the rolls has been used. This is most unsatisfactory since the belt tends to slip on account of the high torque in the system. Positive driving belts or chains have been used, but these have a serious disadvantage in that they are subjected to excessive wear, again on accountof the high torque in the system. Positive gear drive systems have been used but such have the disadvantage that as the centers of the grinding rolls are moved together following wear thereof it is necessary from time to time to change the gear wheels, there being no way of providing easy compensation for the change in distance between the axes of the rolls, as is possible with belts or chains by means of auxilliary jockey pulleys or sprockets.

It is an object of the present invention to provide a drive system for the grinding rolls of a rollermill which overcomes, at least to some extent, the inherent disadvantages of each of the previously used systems described above.

According to the present invention a rollermill having a pair of grinding rolls, one of which is to be driven at a lower speed than the other is characterized in that the drive to the lower speed roll is taken from the higher speed roll by a first drive system having an endless drive transmitting member such as a belt or chain which drives the input shaft of a series connected second drive system comprising a reduction gear-box at a speed higher than that of the higher speed roll, the output shaft of the reduction gear-box being connected with the lower speed roll. The reduction gear-box may be mounted by its output shaft on the shaft of the lowerspeed roll and positioned by means of a torque bar extending between it and a stationary member, or it may be, rockably mounted by resilient means, on a swingable frame carrying the lower roll. It is an object of the invention to maintain the belt or chain tension substantially constant in all relative positions of the grinding rolls.

The invention will be further apparent from the following description with reference to the figures of the accompanying drawings, which show, by way of example only, a rollermill having one form of drive arrangement embodying the invention.

Of the drawing:

FIG. 1 shows a side view of the rollermill;

FIG. 2 shows a fragmentary plan view of the drive arrangement of FIG. 1 substantially on line 2-2 of FIG.

FIG. 3 shows a side view of another embodiment; and

FIG. 4 is a plan view showing an alternative mounting of the gear-box.

Referring now to FIGS. 1 and 2, the rollermill includes parallel upper and lower cylindrical grinding rolls 10 and 11 respectively, stock to be milled being passed through a feed chute 12 for passage through the nip formed between the rolls l0 and 11.

As by a motor indicated at M, roll 10 is positively driven at a required relatively high speed. The lower roll 11 is driven at a predetermined lower speed, the drive for lower roll 11 being derived solely from the upper roll 10 through a belt and pulley system and a reduction gear system connected in series as will appear. Typical speed ratios between the rolls l0. and 11 are 1.25:1 and 2.5:1'for example.

Shaft 21 of upper roll 10 is mounted in fixed bearings in the rollermill casing indicated at 22, so that roll 10 is driven to rotate about a fixed, preferably horizontal, axis.

A swingable support frame 18 is pivoted to the rollermill casing 22 to rock about an axis indicated at 19. Two arms of this frame 18 are shown in FIG. 2. They are rigidly interconnected by cross members (not shown) and both arms are similarly pivoted to the easing, so that the entire frame 18 may be swingably moved about a fixed axis at 19 parallel to the axis of roll 10.

The shaft 23 of lower roll 11 is supported at opposite ends in suitable bearings in the arms of frame 18, and roll 11 is rotatable about an axis parallel to that of roll 10. A motion producing unit 24 mounted on the when mill casing is connected to frame 18 and forms part of a device to selectively swing frame 18 about pivot 19. This unit may for example be a spring unit operated by suitable mechanism, or it may be a suitably controlled double acting reversible fluid pressure responsive ram.

A gear-box 13 consists essentially of a housing 25 and parallel input and output shafts 26 and 27 respectively which are rotatable relative to the housing and drive connected within the housing by a suitable train of reduction gears (not shown). In the illustrated embodiment gearing within the gear-box provides for example a 5:1 speed reduction ratio between shafts 26 and 27. Output shaft 27 is coaxial with and fixed to lower roll shaft 11, and in fact may be integral with shaft 11, and the gearbox 13 is thereby carried by roll shaft 23. A torque bar 14 which may be of adjustable length as illustrated is pivotally connected at opposite ends to the gear-box housing 25 and a stationary part such as the rollermill frame. The torque arm pivots 28 and 29 may be resilient for strain absorbtion, and for example may be rubber bushings or resiliently maintained by springs or fluidic damping devices.

Thus gear-box 13 is thereby mounted solely on the roll shaft 23 and free rotation of the gear-box housing about the axis of shaft 23 is restrained by torque bar 14.

A pulley 15 is secured to input shaft 26 of the gearbox 13 and is adapted to be driven by a belt 16 passing around the same and around a pulley 17 secured on the shaft 21 of the upper roll 10. The ratio of diameters of the pulleys 17 and 15 is such that the input shaft 26 of the gear-box 13 is driven by the belt 16 at a high speed which is however in the illustrated embodiment a predetermined amount less than five times the speed of rotation of the roll 10, whereby, as the gear-box in the given example has a 5:1 reduction ratio, the roll 11 is driven at a speed that is a predetermined amount less than that of the roll and in accordance with the required ratio. Other gear reduction ratios may of course be provided in the gear-box and the factors selected proportionately.

When it is desired to separate rolls 10 and 11 without interrupting the drive to them to adjust the nip upon wear of the rolls or to separate the rolls to their maximum distance apart, unit 24 is actuated to swing frame 18 counterclockwise or downwardly in FIG. 1 about the axis of pivot '19. Since roll 11 is mounted on frame 18 and gear-box 13 is carried by the lower roll shaft 23 both move with frame 18. However since the gear-box housing 25 is held by torque bar 14and is rotatable relative to thegear-box output shaft and roller shaft 23, the gear-box housing will compensatively rock clockwise about the axis of shaft 23.

During this compensative rocking of the gear-box housing relative to and about gear-box output shaft the drive gear train within the housing moves with it and remains operative, the respective meshed gears crawling around each other while transmitting torque, and the dimensions are such that the distance between the axes of pulleys 15 and 17 remains substantially constant even at full separation of rolls 10 and 11. That is to say that, while the movement of frame 18 tends to move the axis of pulley 15 away from the axis of pulley 17, the compensative rocking of the gear-box housing moves the axis of pulley 15 correspondingly toward the axis of pulley 17. During these movements, which are only slight, the tension in the belt 16 remains substantially constant, and any strain on the torque arm 14 is absorbed by the resilient nature of its end connections to the gear-box and the machine frame.

The rolls 10 and 11 may be returned to operative grinding position by reversing the unit 24, frame 18 swinging clockwise about pivot 19 and the gear-box housing rocking oppositely.

In the embodiment of FIG. 3 the corresponding parts are similarly numbered, but here the gear-box 13 is positioned by the torque bar 14 so that its input shaft 26 is well below a line connecting the axes of rolls 10 and 11. In FIG. 1, the gear-box input shaft was above that line.

Operation is substantially the same as in FIG. 1. When it is desired to separate the rolls l0 and 11, ram 24 is operated to moving frame 18 counterclockwise about pivot 19 carrying with it the lower roll 11 and gear-box 13. Here, however, the location of gear-box 13 and the connection to torque bar 14 are such that during movement of gear-box 13 with the frame 18 the box compensatively rocks clockwise about the axis of shaft 23. As in FIGS. 1 and 2, the foregoing movements result in maintaining substantially constant the distance between the axes of pulleys 15 and 17.

The position occupied by the gear-box is entirely one of choice in order to obtain optimum working conditions and to avoid straining the parts as far as possible. Considering the afore-mentioned imaginary line between the shafts of the grinding rolls, if the input shaft 15 is below that line the gear-box will tend to rotate in a clockwise direction upon separation of the rolls, whereas if the input shaft 15 is above the line the rotation will be anti-clockwise. but the result is essentially the same.

With the rolls l0 and 11 either in milling position or separated drive is maintained from motor M through roll 10, shaft 21, pulley 17, belt 16, pulley l5, shaft 26, the gearing within box 13, shafts 27 and 23 to roll I]. The belt and pulley drive at 16 may be replaced by a chain and sprocket drive or like mechanical equivalents.

The foregoing relative movements of the parts are relatively small. In practice, in a cereal milling machine for example, the maximum separation of rolls l0 and 11 is about one-tenth of an inch, and shaft 23 swings about pivot 19 through an arc of only about one degree during separational movement of rolls l0 and 11.

In the foregoing embodiments the force or effective torque in the belt 16 is low, on account of its high speed, the gear-box 13 acting as a torque absorber and minimizing the risk of slippage of the belt 16. The gears within the gear-box 13 move with the roll 11 and do not therefore require replacement when the distance between the axes of the rolls 10 and 11 is decreased to compensate for wear of the rolls. Should it be necessary to adjust the tension in the belt 16, this is readily done by changing the effective length of the adjustable torque bar 14.

FIG. 4 illustrates an embodiment which as indicated by similar numerals has most of the same parts in the same relation as FIG. 1, but wherein the gear-box 13, instead of floating freely on its output shaft as in FIGS. 1-3, is mounted on frame 18 by resilient means permitting slight rocking about the axis of shaft 23. The end of shaft 23 is rotatably mounted on frame 18 in a bearing unit having a casing 30 rigid with frame 18. A resilient bushing 31 consisting of concentric inner and outer metal shells 32 and 33 and an intermediate molded rubber sleeve 34 has the inner shell fixed on casing 30 and the outer shell fixed on gear-box 13.

Bushing 31 is preferably of the type wherein sleeve 34 is in partially permanent compression. Bushings of this type are well known per se, being made. by first molding the rubber sleeve between the concentric metal shells and then substantially enlarging the diameter of the inner shell, which of course is preferably of ductile metal, thus compressing the rubber sleeve.

During assembly on frame 18 the gear-box is mounted offset slightly counterclockwise relative to its position in operation and the bushing unit is tensioned by rocking the gear-box toward that position until belt 16 is placed over pulley 15. Then upon release and return of the gear-box the belt 16 will be under required tension. When the rolls are to be separated by swinging frame 18 about pivot 19 tension produced in sleeve 34 tends to compensatively rock the gear-box 13 clockwise about the axis of shaft 23, which slightly reduces the compression in sleeve 34 but some positive compression remains. The distance between the axes of pulleys 17 and 15 is retained substantially constant as in FIGS. 1-3.

In appearance a side elevation of the embodiment of FIG. 4 would be essentially that of FIG. 1, except that by rockably mounting the gear-box on the frame 18 by resilient means, as above explained, the torque bar 14 may be eliminated. Gear-box 13, in the FIG. 4 embodiment, may be positioned as in FIG. 1 or FIG. 3.

It should be noted that if it is desired to change the ratio between the speeds of the rolls l0 and 11 in any embodiment this is easily done by changing one or both of the pulleys 17 and 15, the remainder of the drive system remaining undisturbed.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A rollermill having a pair of grinding rolls, one of which is driven at a required relatively high speed, and means for driving the other roll from said one high speed roll at a predetermined lower speed, characterized by means providing a desired ratio of speeds between said rolls comprising a reduction gear-box having an input shaft connected through an endless drive transmitting member to be driven from said high speed roll at a speed higher than that of said high speed roll and an output shaft driven at said lower speed connected to drive said lower speed roll at said lower speed.

2. A rollermill according to claim 1 wherein said reduction gear-box is mounted by its output shaft on a shaft carrying the lower speed roll.

3. A rollermill according to claim 1, wherein the lower speed roll and said gear-box are mounted on a pivoted member and means is provided for swinging said pivoted member between positions where said two grinding rolls are respectively operatively engaged and separated, and wherein means is provided such that, when the said rolls are so separated, the distance between the axes of the high speed roll and the input shaft of the gear-box remains substantially constant and substantially constant tension is maintained in said endless drive transmitting member.

4. A rollermill according to claim 3, wherein said last named means comprises a torque bar extending between the gear-box and a stationary member.

5. A rollermill as defined in claim 3, wherein said last named means comprises means resiliently mounting said gear-box on said pivoted member for rocking substantially concentrically of the axis of said output shaft of the gear-box 6. A rollermill comprising a pair of grinding rolls, means for driving one of said rolls at a predetermined relatively high speed and means for driving the other of said rolls from said one roll at a desired lower speed comprising a first drive system having an endless drive member connected to be driven by said one roll and a second drive system in series therewith having an input shaft driven by said endless drive member and connected by gearing to an output shaft parallel to and radially spaced from said input shaft and coaxially connected to said other roll, and means for adjusting the spacing between said rolls while maintaining drive transmission between them and maintaining the distance between the axis of said one roll and the axis of said input shaft substantially constant for retaining substantially constant tension in said endless drive memher.

7. A rollermill as defined in claim 6, wherein said first drive system comprises an endless belt disposed between pulleys on said one roll and said gearing system input shaft.

8. A rollermill as defined in claim 6, wherein said last named means comprises a pivoted frame on which said other roll is rotatably mounted and means for controllably pivoting said frame to change the roll spacing, and said second drive system comprises a gear-box supported on said other roll for movement therewith about the axis of said output shaft, and means is provided whereby said gear-box is rocked compensatively aboutthe axis of said output shaft during movement of said frame for maintaining said distance substantially constant.

9. A rollermill as defined in claim 8, wherein said gear-box is rockably supported by means of said output shaft on said other roll.

10. A rollermill as defined in claim 9, wherein a torque arm connects said gear-box to a fixed part for effecting said compensative rocking.

11. The rollermill defined in claim 8 wherein said gear-box is rockably supported by means of a resilient annular bushing on said frame.

12. The rollermill defined in claim 11, wherein said bushing comprises a precompressed annular sleeve of resilient material.

13. The rollermill defined :in claim 6, wherein said first system drives said input shaft at a predetermined higher speed than said one roll and said gearing provides a predetermined speed reduction between said input and output shafts whereby to drive said other roll at said desired lower speed.

14. The rollermill defined in claim 13, wherein the drive speed ratio provided by said reduction gearing is about five to one and wherein said first system drives said input shaft at a speed slightly less than five times the speed of said one roll so that the speed of said other roll is a predetermined amount less than that of said one roll, for obtaining a speed ratio between said rolls of about 1.25:1 to 2.50:1. 

1. A rollermill having a pair of grinding rolls, one of which is driven at a required relatively high speed, and means for driving the other roll from said one high speed roll at a predetermined lower speed, characterized by means providing a desired ratio of speeds between said rolls comprising a reduction gear-box having an input shaft connected through an endless drive transmitting member to be driven from said high speed roll at a speed higher than that of said high speed roll and an output shaft driven at said lower speed connected to drive said lower speed roll at said lower speed.
 2. A rollermill according to claim 1 wherein said reduction gear-box is mounted by its output shaft on a shaft carrying the lower speed roll.
 3. A rollermill according to claim 1, wherein the lower speed roll and said gear-box are mounted on a pivoted member and means is provided for swinging said pivoted member between positions where said two grinding rolls are respectively operatively engaged and separated, and wherein means is provided such that, when the said rolls are so separated, the distance between the axes of the high speed roll and the input shaft of the gear-box remains substantially constant and substantially constant tension is maintained in said endless drive transmitting member.
 4. A rollermill according to claim 3, wherein said last named means comprises a torque bar extending between the gear-box and a stationary member.
 5. A rollermill as defined in claim 3, wherein said last named means comprises means resiliently mounting said gear-box on said pivoted member for rocking substantially concentrically of the axis of said output shaft of the gear-box.
 6. A rollermill comprising a pair of grinding rolls, means for driving one of said rolls at a predetermined relatively high speed and means for driving the other of said rolls from said one roll at a desired lower speed comprising a first drive system having an endless drive member connected to be driven by said one roll and a second drive system in series therewith having an input shaft driven by said endless drive member and connected by gearing to an output shaft parallel to and radially spaced from said input shaft and coaxially connected to said other roll, and means for adjusting the spacing between said rolls while maintaining drive transmission between them and maintaining the distance between the axis of said one roll and the axis of said input shaft substantially constant for retaining substantially constant tension in said endless drive member.
 7. A rollermill as defined in claim 6, wherein said first drive system comprises an endless belt disposed between pulleys on said one roll and said gearing system input shaft.
 8. A rollermill as defined in claim 6, wherein said last named means comprises a pivoted frame on which said other roll is rotatably mounted and means for controllably pivoting said frame to change the roll spacing, and said second drive system comprises a gear-box supported on said other roll for movement therewith about the axis of said output shaft, and means is provided whereby said gear-box is rocked compensatively about the axis of said output shaft during movement of said frame for maintaining said distance substantially constant.
 9. A rollermill as defined in claim 8, wherein said gear-box is rockably supported by means of said output shaft on said other roll.
 10. A rollermill as defined in claim 9, wherein a torque arm connects said gear-box to a fixed part for effecting said compensative rocking.
 11. The rollermill defined in claim 8 wherein said gear-box is rockably supported by means of a resilient annular bushing on said frame.
 12. The rollermill defined in claim 11, wherein said bushing comprises a precompressed annular sleeve of resilient material.
 13. The rollermill defined in claim 6, wherein said first system drives said input shaft at a predetermined higher speed than said one roll and said gearing provides a predetermined speed reduction between said input and output shafts whereby to drive said other roll at said desired lower speed.
 14. The rollermill defined in claim 13, wherein the drive speed ratio provided by said reduction gearing is about five to one and wherein said first system drives said input shaft at a speed slightly less than five times the speed of said one roll so that the speed of said other roll is a predetermined amount less than that of said one roll, for obtaining a speed ratio between said rolls of about 1.25:1 to 2.50:1. 